Direct access storage devices (DASD) have become part of every day life, and as such, expectations and demands continually increase for better performance at lower cost. To meet these demands, the mechano-electrical assembly in a DASD device, specifically the Hard Disk Drive (HDD) has evolved to meet these demands.
In order for an HDD to hold more data, advances in the magnetic transducer as well as the disk media on which the data is written have undergone major advances in the past few years. A critical relationship between the magnetic transducer and disk is the spacing between their adjacent surfaces. This is typically known as the fly height.
The magnetic transducer flies proximately to the disk by virtue of an air film created by the disk spinning next to a pattern on the surface of the HDD slider (and magnetic transducer contained there within). This pattern on the HDD slider is known as the air-bearing surface, or ABS. The ABS is fabricated on the surface of the slider that is closest to the disk. Typically the magnetic transducer resides at the end of the slider known as the trailing edge of the slider, so called the trailing edge because it is the last edge of the slider to fly proximately to the disk.
Control of the fly height is critical to the density of data that can be written onto the disk surface. Once the slider is flying above the disk surface, maintaining the desired fly height is critical to the operation of the HDD. Several conditions can arise that can change the fly height of the slider. The following examples are not intended to be an all-inclusive list of conditions that can affect fly height. These few examples are presented only for the sake of illustration, brevity and clarity. Mechanical shock entering the HDD can cause the ABS to become unstable and lose its ability to fly the slider properly. Debris can interact with the slider and change its fly height.